Nitrogen, phosphorus and potassium - the most important plant nutrients - are the focus of this issue paper. However, a host of other nutrients are important in the production of quality food.

Fertilizers feed the plants that feed the world

Plant health, productivity and nutritional content are substantially influenced by the presence of a correct balance of available essential nutrients. The use of mineral fertilizers is intended to correct natural imbalances or deficiencies in plant nutrients. Plants cannot distinguish between essential nutrients provided by mineral fertilizers or "organic" sources. However, it is easier to ensure a balanced, adequate supply of nutrients by applying mineral fertilizers. Integrating them with organic manures and legumes within comprehensive plant nutrition systems tailored to local circumstances is the key to sustained soil fertility.

The use of mineral fertilizers in food crop production poses little risk for human consumption. In some cases, naturally occurring metal impurities or radioactive elements, which may be present in fertilizers, can accumulate in soils. Their effects can be mitigated by adopting soil management practices that minimize plant uptake, selecting plant varieties that limit accumulation, using sources lower in impurities and monitoring levels to avoid build-up concerns. Animal manures may contain as much, if not more, of these impurities.

Nutritional value, appearance and taste are also important factors that determine overall food quality. Vitamins and micronutrients in food are important for health and human development, and deficiencies constitute a major problem in some regions. Fertilizers contain elements that influence plant growth, which ultimately produce healthy crops. The use of fertilizers may also influence appearance by favouring root development, drought resistance, plant growth and ripening - all factors in the final quality of food. Texture, firmness and resistance to transport damage may be enhanced by the application of the right balance of mineral fertilizers. Plant nutrients may affect the taste of food by influencing its chemical composition - including its acidity or sweetness. Proper, balanced plant nutrition avoids crop quality disorders and improves resistance to stress, caused, for example, by drought, frost and pests and diseases. The concurrent application of phosphate, potash and sulphur improves the nutrient utilization efficiency of nitrogen.

In its nitrate form, nitrogen is highly soluble and therefore may leach into groundwater if plants do not efficiently absorb it. Nitrate intake - from fertilizer use or naturally occurring sources - has in the past been associated with the formation of nitrite in the human intestinal tract.
However, increasing evidence is now emerging that human intestinal conditions do not favour the formation of nitrite and the negative health effects associated with them. There is, in fact, evidence that some nitrate is beneficial to human health, as it seems to act as a protection against many pathogens. In normal amounts, phosphorus is an important constituent of all living organisms. Excessive phosphorus enrichment can cause biological imbalances in fresh water. However, this phenomenon is only marginally related to mineral fertilizer use, and losses are minimized when phosphorus is applied in appropriate amounts. Potassium has no adverse impact on human health at the concentration found in groundwater. Milk and vegetables frequently contain more potassium than water, and this mineral seems to play an important role in controlling hypertension.

IFA advocates the responsible and efficient use of mineral fertilizers to:

• raise yields and thus the availability of food for a growing population,
• improve the quality of crops,
• increase the nutritional value of food crops.

IFA encourages stewardship in the production and consumption of fertilizers to maximize the benefits of fertilizer use for human health.

IFA is committed to working with other stakeholders to achieve these goals.

November 2001